[pypy-commit] pypy default: if start - stop <= 0, return a empty string

[gutworth]

Author: Benjamin Peterson <benjamin at python.org>
Branch: 
Changeset: r54052:3b13b7c4c388
Date: 2012-03-28 22:48 -0400
http://bitbucket.org/pypy/pypy/changeset/3b13b7c4c388/

Log:	if start - stop <= 0, return a empty string

diff --git a/pypy/rpython/lltypesystem/rstr.py b/pypy/rpython/lltypesystem/rstr.py
--- a/pypy/rpython/lltypesystem/rstr.py
+++ b/pypy/rpython/lltypesystem/rstr.py
@@ -765,7 +765,8 @@
     def _ll_stringslice(s1, start, stop):
         lgt = stop - start
         assert start >= 0
-        assert lgt >= 0
+        if lgt <= 0:
+            return s1.empty()
         newstr = s1.malloc(lgt)
         s1.copy_contents(s1, newstr, start, 0, lgt)
         return newstr
diff --git a/pypy/rpython/test/test_rstr.py b/pypy/rpython/test/test_rstr.py
--- a/pypy/rpython/test/test_rstr.py
+++ b/pypy/rpython/test/test_rstr.py
@@ -477,7 +477,8 @@
             s1 = s[:3]
             s2 = s[3:]
             s3 = s[3:10]
-            return s1+s2 == s and s2+s1 == const('lohel') and s1+s3 == s
+            s4 = s[42:44]
+            return s1+s2 == s and s2+s1 == const('lohel') and s1+s3 == s and s4 == ""
         res = self.interpret(fn, [0])
         assert res